UNIVERSITY   OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL   EXPERIMENT  STATION 

CIRCULAR  No.  258 
March,  1923 

THINNING  DECIDUOUS  FRUITS 

By  WAEEEN  P.  TUFTS 


The  deciduous  fruits  of  California  are  famed  for  their  excellence. 
To  maintain  this  reputation  in  view  of  the  increasing  tonnage,  it  is 
necessary  to  give  careful  attention  to  all  the  factors  that  combine 
to  make  a  perfect  product.  Size,  color,  texture  and  flavor  are  the 
chief  points  sought  for  and  these  taken  together  go  to  make  up  the 
somewhat  elusive  term  known  as  quality. 

Thinning  the  immature  fruit  is  one  of  the  most  essential  orchard 
operations  because  crowded  fruit  cannot  size  properly  and  neither 
will  the  color,  texture  and  flavor  be  of  the  best.  Considerable  thinning 
is  done  when  the  trees  are  pruned.  These  two  operations  are  there- 
fore so  closely  related  that  one  cannot  be  discussed  without  a  con- 
sideration of  the  other. 

Little  experimental  data  exist  for  guidance  in  thinning.  Most 
growers,  however,  have  demonstrated  to  their  satisfaction  that  the 
operation  pays.  This  is  particularly  true  with  apricots,  peaches  and 
shipping  plums.  It  is  the  aim  of  this  circular  to  present  as  briefly 
as  possible  certain  general  considerations  as  well  as  practical  sug- 
gestions for  the  carrying  out  of  the  work. 

SPECIFIC    RECOMMENDATIONS 

Almond. — The  almond  is  not  generally  thinned.  However,  cer- 
tain growers  report  success  in  removing  a  portion  of  the  crop  shortly 
after  the  seeds  begin  to  harden  to  sell  to  the  " green  almond"  market, 
the  remaining  nuts  being  left  to  attain  greater  size  and  weight.  The 
practice  is  not  well  enough  established  to  recommend  its  adoption, 
especially  since  the  outlet  for  the  green  fruit  is  restricted. 

Apple. — The  fruit-bud  of  the  apple  produces  a  cluster  of  flowers, 
several  of  which  usually  set  fruit,  but  only  one  as  a  rule  should  be 
left  at  thinning  time.  When  there  is  a  heavy  set  some  spurs  must 
be  deprived  of  all  their  fruit  so  that  when  the  apples  are  ripe  they 
will  be  from  four  to  six  inches  apart  on  the  branch.     Some  varieties 


Z  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

such  as  the  Winesap,  must  be  thinned  even  more  severely  so  that 
the  fruits  possibly  are  not  closer  than  eight  or  ten  inches.  When 
the  crop  is  not  so  heavy  and  growing  conditions  are  favorable,  then 
it  may  be  permissable  to  leave  two  specimens  to  the  spur. 

Apples  should  generally  be  thinned  immediately  after  the  June 
drop.  However,  under  certain  conditions  and  with  some  varieties, 
notably  the  earlier  maturing  sorts,  by  delaying  the  thinning  for  a 
time  it  has  been  found  possible  to  profitably  dispose  of  the  immature 
fruit  for  culinary  purposes  and  at  the  same  time  secure  proper  devel- 
opment of  the  main  crop. 

Specially  designed  ''thinning  shears"  are  on  the  market  for  use 
in  apple  thinning,  but  the  use  of  these  with  most  varieties  will  not 
prove  faster  than  removal  by  hand.  Furthermore,  there  is  danger 
of  injuring  the  specimens  left  with  the  sharp  points  of  the  shears. 

Apricot. — Apricots  should  be  thinned  so  that  no  two  specimens 
will  touch  when  ripe.  Ordinarily  the  young  fruits  should  not  be  left 
closer  than  from  three  to  five  inches  on  strong  shoots  and  only  one 
fruit  to  each  short  spur.  Two  fruits  may  be  left  near  together  on 
opposite  sides  of  the  branch  or  even  on  a  short  spur,  if  no  other  fruits 
are  closer  than  four  or  five  inches. 

In  the  coast  sections  where  brown  rot  is  prevalent,  great  care 
should  be  taken  to  see  that  fruits  do  not  touch  when  ripening.  In 
clusters  of  apricots  there  is  often  enough  moisture  between  fruits  that 
touch  each  other,  to  germinate  spores  of  the  brown  rot.  This  disease 
spreads  very  quickly  from  fruit  to  fruit  at  ripening  time,  by  contact, 
and  within  two  or  three  days  the  entire  cluster  may  be  infected. 

Thinning  apricots  on  trees  which  have  been  pruned  by  the  so- 
called  ' '  long  system ' '  requires  special  mention.  Such  trees  ordinarily 
set  a  much  heavier  crop  than  "short  pruned"  trees  of  similar  age 
and  therefore  require  heavier  thinning.  In  some  sections  apricot 
trees  set  fruit  on  the  slender  one-year  shoots  which  if  left  is  very 
likely  to  produce  small,  scarred  and  "fog-marked"  specimens.  These 
should  all  be  removed  and  this  is  most  easily  and  cheaply  accom- 
plished by  means  of  a  light  pole  to  the  end  of  which  has  been  fastened 
twelve  or  fourteen  inches  of  old  rubber  hose.  The  branches  may  be 
struck  with  this  hose  to  knock  off  the  apricots  at  thinning  time  with- 
out material  injury  to  either  branch  or  buds. 

Considerable  experience  is  necessary  to  determine  how  heavy  the 
set  must  be  to  make  a  systematic  thinning  of  the  apricot  orchard 
economical.  Observations  seem  to  indicate  that  crops  up  to  a  certain 
tonnage  will  be  brought  through  to  maturity  with  marketable  sizes 


Circular  258] 


THINNING  DECIDUOUS   FRUITS 


Fig.  1.— Cluster  of   apples  setting  from    one   fruit-bud.      For   best   results 
only  one  fruit  should  remain  after  thinning. 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

without  carefully  breaking  up  every  cluster  and  separating  adjacent 
fruits  as  above  recommended.  Nevertheless,  conservative  apricot 
growers  make  thinning  one  of  their  annual  orchard  operations. 

Table  1  gives  the  results  of  a  thinning  experiment  on  apricots 
conducted  by  V.  C.  Blanchard  of  the  Agricultural  Extension  Services 
in  Los  Angeles  County  during  the  season  of  1922. 

Table  1 

Hand  Thinning  of  Apricots 

Parmentier  orchards,  San  Fernando  Valley,  1922 

Thinning  Size  Yield 


Proportion  of  fruit  Fruits  per  Pounds  per 

Pruning  Treatment  removed  pound  tree 

Thinned  only  (long) One-half 9-10  300 

Heavy  heading  (short) Clusters — One-third 14-15  240 

None None 17-18  200 

Thinned  only  (long) Terminals  only 12  (No  data) 

The  lightly  pruned  trees  set  very  abundantly  and  at  thinning 
time  it  was  thought  desirable  to  remove  approximately  one-half  of 
the  fruit.  That  this  treatment  was  advisable  is  shown  by  the  size  of 
the  individual  fruits  harvested  as  well  as  by  the  total  yield.  Heavy 
pruning,  resulting  in  less  fruit — all  borne  in  dense  clusters — gave 
less  yield  and  smaller  sizes.  The  smallest  fruit  and  crop  was  pro- 
duced by  trees  receiving  neither  pruning  nor  thinning.  In  the  case 
where  a  thinning  method  of  pruning  was  accompanied  by  the  removal 
of  fruit  from  only  the  terminal  growths,  the  size  of  the  individual 
specimens  was  quite  satisfactory.  Unfortunately  this  tree  was  har- 
vested without  the  weight  of  the  crop  being  secured.  This  latter 
method  of  thinning,  however,  is  not  to  be  generally  recommended. 

Cherry. — The  cherry  is  not  thinned. 

Peach. — The  peach  responds  most  readily  of  all  the  deciduous 
fruits  to  thinning  and  is  the  one  fruit  which  under  practically  all 
conditions  must  be  thinned.  It  has  been  shown  that  it  takes  two 
two-inch  peaches  to  equal  in  "green"  weight  one  two-and-a-half -inch 
peach,  and  also  that  when  the  dried  fruit  is  considered  it  takes  three 
and  three-quarter  standard  grade  Muirs  to  equal  one  extra  fancy 
dried  Muir.     These  facts  emphasize  the  importance  of  securing  size. 

The  common  recommendation  has  been  to  thin  peaches  so  that 
the  fruits  are  separated  by  four  to  six  inches  at  ripening.  However, 
if  two  fruits  are  on  opposite  sides  of  a  shoot  and  are  far  removed 
from  other  specimens  both  may  be  left.  It  is  probably  impractical 
in  most  cases  to  attempt  to  separate  "doubles."  Remove  all  such 
if  there  are  enough  "singles"  to  make  a  crop. 


Circular  258] 


THINNING  DECIDUOUS  FRUITS 


Fig.    2. — Fruits    composing    this    cluster    of    apricots    would    have    reached 
better  size  had  one  or  two  specimens  been  removed  at  thinning. 


b  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Recently  Weldon*  has  submitted  figures,  collected  by  the  Southern 
California  Canners'  Bureau  and  the  California  Growers'  Association, 
showing  the  number  of  peaches  of  different  sizes  necessary  to  make 
a  ton  of  fresh  fruit.  From  these  facts  the  author  calculates  the 
number  of  peaches  of  a  given  size  which  must  be  left  on  a  single  tree 
planted  at  a  certain  distance  to  produce  a  given  tonnage  per  acre. 


Number  of  tons  per  acre 
desired 

Tons 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 


Table  2 
Thinning  Schedule 

Number  of  peaches  per  tree,  of  234  in.,  2%  in.  and  2%  in.,  sizes  to 
produce  des'red  tonnage  per  acre  as  shown  in  left  hand  column, 
from  trees  planted  the  different  distances  indicated  below. 


20  feet  x  20  feet 
108  trees  per  acre 

24  feet  x  24  feet 
75  trees  per  acre 

2Min. 

2V2  in. 

2H  in. 

2^in. 

2Y2  in.         : 

1%  in. 

104 

70 

54 

149 

101 

77 

208 

140 

108 

298 

202 

154 

312 

210 

162 

447 

303 

213 

416 

230 

216 

596 

404 

308 

520 

350 

270 

745 

505 

385 

624 

420 

324 

894 

606 

462 

728 

490 

378 

1043 

707 

539 

832 

550 

432 

1192 

808 

616 

936 

630 

483 

1341 

909 

693 

1040 

700 

540 

1490 

1010 

770 

The  orchardist  can  only  after  long  years  of  experience  accurately 
estimate  the  tonnage  trees  of  a  certain  age  and  condition  should  pro- 
duce. Reducing  the  number  of  peaches  on  a  tree  to  a  given  number 
will  not  assure  the  grower  that  a  given  size  will  be  reached.  Age 
of  trees,  soil  and  moisture  conditions,  pest  control  and  pruning  treat- 
ment all  must  be  taken  into  account  when  utilizing  any  such  method 
as  outlined  above. 

Tear. — Pears  are  not  generally  thinned  in  California.  It  would 
seem,  however,  that  where  conditions  are  not  entirely  ideal  that  the 
same  considerations  should  hold  with  the  pear  as  with  the  apple. 
In  sections  where  the  fruit  which  ripens  first  is  shipped,  it  has  been 
the  common  experience  that  the  removal  of  the  earlier  maturing 
specimens  helps  materially  in  sizing  the  balance  of  the  crop.  This 
fact  is  especially  true  of  the  Bartlett  variety.  Very  large  sizes  are 
undesirable  for  either  shipping  or  canning  and  should  be  dried. 


*  Geo.  P.  Weldon,  A  New  Idea  in  Peach  Thinning.     Bull.  No.  5,  Feb.,  1923, 
Chaffey  Junior  College,  Ontario,  Calif. 


Circular  258] 


THINNING  DECIDUOUS   FRUITS 


Fig.  3. — Ideal  distribution  of  apricots  on  small  one-year-old  fruiting  shoot. 


8  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Plum  and  Prune. — Plums,  especially  those  intended  for  "green" 
shipment,  should  always  be  thinned.  This  is  particularly  true  of  the 
Japanese  varieties  which  normally  fruit  so  abundantly.  Plums  should 
ordinarily  be  separated  from  one  to  three  inches  when  fully  mature. 
Varieties  belonging  to  the  European  species  will  as  a  rule  size  better 
in  dense  clusters  than  will  the  Japanese  sorts. 

It  has  not  been  found  economical  to  do  any  thinning  of  plum 
varieties  utilized  for  prune  making  other  than  that  accomplished  at 
the  annual  pruning.  There  is,  however,  one  possible  exception  to  the 
statement  just  made,  namely,  the  Sugar  prune.  As  grown  in  certain 
localities,  this  variety  must  be  thinned  to  prevent  overbearing  with 
resultant  breakage  of  branches — the  wood  of  the  Sugar  prune  being 
exceedingly  brittle — and  to  offset  a  decided  tendency  towards  "alter- 
nate bearing." 

REASONS    FOR    THINNING 

Thinning  may  be  defined  as  the  removal  of  a  certain  portion  of 
the  fruit  crop  from  the  tree  in  order  to : 

1.  Improve  size,  color,  texture,  flavor  and  individual  uniformity. 

2.  Prevent  breakage  of  trees  by  better  distribution  of  crop. 

3.  Reduce  disease  and  insect  injury. 

4.  Maintain  vigor  of  the  tree. 

5.  Secure  more  regular  bearing. 

6.  Decrease  labor  of  handling  crop. 

It  has  been  the  common  experience  of  growers,  and  many  actual 
tests  have  shown,  that  where  there  is  a  heavy  set  of  fruit  the  reduction 
of  the  number  "of  specimens  will  as  a  rule  result  in  better  average 
size,  color  and  uniformity  and  enhance  the  general  attractiveness  of 
the  entire  crop. 

Frequently,  either  on  account  of  improper  thinning  of  fruiting 
wood  at  the  dormant  pruning,  or  an  unusually  favorable  season  for 
fruit  setting  trees  may  be  so  loaded  that  much  breakage  will  result 
uniess  the  weight  of  the  crop  is  reduced  by  thinning. 

Certain  diseases  and  insects  flourish  where  fruit  is  closely  crowded 
on  the  branch.  In  order  to  control  these  pests  it  is  necessary  to  break 
up  the  clusters.  The  codling  moth,  which  causes  wormy  apples  and 
pears  delights  in  making  its  entrance  where  two  fruits  touch.  Brown 
rot  of  the  stone  fruits  is  more  rapidly  spread  when  the  fruit  hangs 
in  dense  clusters  or  even  touches. 

Bigelow  and  Gore*  a  number  of  years  ago  reported  the  average 
composition  of  six  varieties  of  peaches  at  different  stages  of  growth. 
The  results  are  given  in  table  3. 

*  Bigelow,  W.  D.,  and  Gore,  H.  C,  U.  S.  Dept.  Agr.  Bur.  Chem.,  Bull.  97,  1905. 


Circular  258] 


THINNING  DECIDUOUS  FRUITS 


Fig.  4. — Ideal  distribution  of  apricots  when  borne  on  adjacent  short  spurs. 


10 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Table  3 

Average  Composition  of  Six  Varieties  of  Peaches  at  Different 
Stages  of  Growth 


Weight  of 


Total  Solids  in 


Peach  Flesh  Stone  Kernel 

Stage  of  growth          Grams  Per  cent  Per  cent  Per  cent 

June  Drop 9.51  64.55  32.50  2.94 

Stone  Hardened...     16.75  71.54  25.82  2.89 

Market-ripe 73.59  92.49  6.86  0.65 


Flesh 
Per  cent 

14.77 
16.97 
14.04 


Stone 
Per  cent 

9.37 
27.35 
66.94 


Kernel 
Per  cent 

6.89 
7.54 

44.78 


A  study  of  the  foregoing  figures  discloses  several  interesting  facts. 
The  proportion  of  total  solids  in  the  pits  (stone  and  kernel)  of  the 
peach,  even  at  a  relatively  early  stage  of  development,  is  compara- 
tively great.  From  this,  it  may  probably  be  safely  concluded  that 
the  bringing  to  maturity  of  a  large  number  of  pits  is  a  greater  drain 
upon  the  tree  than  the  ripening  of  a  smaller  number  of  fruits,  which 
on  account  of  larger  size,  aggregate  the  same  weight.  It  is  a  matter 
of  common  knowledge  that  the  size  of  the  pit  in  the  stone  fruits  varies 
very  little  between  large  and  small  specimens  of  the  same  variety. 
Inasmuch  as  the  solids  in  the  pits  are  proportionately  much  less 
before  the  stone  hardens  it  would  seem  desirable  to  thin  as  soon  as 
possible  after  all  natural  shedding  of  superfluous  fruits  has  stopped. 
These  facts  would  seem  to  indicate  that  the  vigor  of  the  tree  may  be 
maintained  by  judicious  thinning. 

Many  statements  have  in  the  past  been  made  to  the  effect  that 
thinning,  by  not  allowing  all  spurs  to  produce  any  one  season,  will 
prevent  the  alternation  of  bearing  which  seems  to  be  the  fixed  habit 
of  some  apple  and  pear  varieties.  Carefully  checked  experiments 
have  shown  this  assumption  to  be  incorrect,  except  in  so  far  as  a 
heavy  crop  one  year  tends  to  deplete  the  resources  of  the  trees  for 
the  following  season.  With  the  stone  fruits  a  very  heavy  produc- 
tion one  year  is  almost  always  followed  by  a  light  crop  the  next  unless 
utmost  care  is  taken  with  all  orchard  operations. 

Thinning  so  as  to  decrease  the  number  of  fruits  to  be  handled  at 
harvest  time  materially  reduces  picking,  grading  and  packing  costs. 
Lessening  the  number  of  fruits  does  not  necessarily  mean  less  tonnage. 
Thinning  is  apt  to  result  in  considerable  increase  in  size.  The  can- 
ners  of  California  have  adopted  as  a  slogan,  "one  two-and-a-half- 
inch  peach  weighs  as  much  as  two  two-inch  peaches." 


Circular  258] 


THINNING  DECIDUOUS  FRUITS 


11 


Fig.  5. — Apricots  on  opposite  sides  of  spur  which  should  reach  good  market 
able  size.     Note  distance  from  other  fruit. 


12  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

GENERAL    CONSIDERATIONS 

The  fruit  tree  utilizes  all  its  energies  in : 

1.  Wood  growth. 

2.  Fruit  and  seed  production. 

3.  Fruit-  and  leaf-bud  formation. 

4.  Manufacture  and  storage  of  reserve  food  materials. 

Of  the  different  orchard  operations  which  modify  these  life 
processes  probably  no  other  one  has  such  a  profound  and  immediate 
influence  as  pruning.  Any  pruning  system  (such  as  the  one  which 
has  been  so  widely  recommended  by  the  University  of  California 
during  the  last  few  years),  which  results  in  a  greater  storage  of  plant 
food  reserves,  the  formation  of  more  fruit-spurs  and  fruit-buds,  and 
consequent  modification  of  new  wood  growth,  is  most  intimately 
associated  with  the  question  of  fruit  thinning.  In  fact,  the  thinning 
of  the  fruit  is  an  integral  part  of  the  pruning  system. 

Plant  food  materials  before  being  assimilated  by  the  tree  in 
carrying  on  its  activities,  must  be  transformed  in  the  leaves  into 
rather  complex  plant  foods  and  there  is  some  evidence  to  show  that 
much  of  this  food  is  utilized  near  the  point  of  manufacture.  Having 
this  fact  in  mind,  it  may  be  argued  that  more  fruit  can  be  brought 
to  a  satisfactory  maturity  on  shoots  or  spurs  having  a  comparatively 
large  leaf  area.  Field  observation  offers  convincing  proof  of  the 
correctness  of  this  assumption. 

Young  trees,  especially  with  a  vigorous  vegetative  growth,  tend 
to  set  fewer  fruits  than  slower  growing  mature  ones,  and  as  a  rule 
need  less  thinning.  There  is  likewise  a  distinct  varietal  difference 
in  the  ability  of  the  various  sorts  to  size  their  crops.  The  Winesap 
variety  of  apple,  for  example,  needs  far  more  thinning  than  the 
average. 

Soil  and  moisture  conditions  must  be  favorable.  Thinning  cannot 
be  made  to  atone  for  poor  cultural  treatment.  Naturally  more  fruit 
may  be  left  under  ideal  conditions  than  where  there  is  a  deficiency 
in  either  soil  moisture  or  fertility.  Also  it  should  be  stated  in  passing 
that  during  the  early  development  of  the  fruit,  should  there  be  a  lack 
of  available  moisture  in  the  soil,  the  leaves  have  the  ability  of  with- 
drawing water  from  the  fruit.  This  condition  may  readily  proceed 
so  far  that  the  fruit  is  unable  to  recover  even  with  copious  irrigations 
at  a  later  date.    Keep  the  soil  moisture  at  the  optimum  at  all  times. 


Circular  258]  THINNING  DECIDUOUS  FRUITS  13 

Much  of  the  thinning  work  may  be  accomplished  at  the  annual 
dormant  pruning,  at  less  expense,  by  the  judicious  selection  and 
distribution  of  fruiting  wood.  With  certain  fruits,  however,  even 
with  tha  most  careful  pruning,  a  portion  of  the  fruit  must  be  removed 
after  the  first  and  second  ' '  drops ' '  or  the  trees  will  tend  to  overbear. 
Attempts  at  thinning  the  fruit  at  pruning  time  in  some  localities 
where  there  is  more  or  less  of  a  frost  hazard,  may  result,  in  unfavor- 
able seasons,  in  greatly  reduced  crops. 

It  has  already  been  pointed  out  that  thinning  is  best  done  as 
early  in  the  spring  as  the  habit  of  natural  dropping  permits.  This 
will  vary  for  different  localities  and  fruits.  The  so-called  "June 
drop"  in  reality  in  many  fruit  sections  of  California  takes  place  in 
April  or  May.  A  satisfactory  explanation  of  this  phenomenon  has 
yet  to  be  proved  experimentally. 

The  actual  operation  of  thinning  is  accomplished  in  various  ways 
in  the  different  fruit  districts  of  the  state.  The  only  satisfactory  way 
is  removal  of  the  undesirable  fruit  with  the  hand,  never  by  shaking 
or  knocking  with  a  pole.  By  the  latter  methods  fruit-spurs  are 
broken,  even  spacing  of  fruit  left  is  impossible,  and  no  discrimination 
can  be  made  between  good  and  bad  specimens.  Fruit  made  unsalable 
by  insect  injuries,  plant  diseases,  frost  and  mechanical  malformations 
can  be  removed  when  thinning  is  done  by  hand;  otherwise  many  of 
these  specimens  will  remain  on  the  trees  until  harvest  and  the  hand- 
ling of  these  culls  will  impose  a  further  burden  at  a  very  busy  season. 


STATION  PUBLICATIONS  AVAILABLE  FOR  FREE  DISTRIBUTION 


BULLETINS 


No. 

253.  Irrigation  and  Soil  Conditions  in  the 
Sierra  Nevada  Foothills,  California. 

261.  Melaxuma    of    the    Walnut,     "Juglans 

regia." 

262.  Citrus   Diseases   of   Florida    and    Cuba 

Compared  with  those  of  California. 

263.  Size  Grades  for  Ripe  Olives. 

268.   Growing  and  Grafting  Olive  Seedlings. 

270.  A  Comparison  of  Annual  Cropping,  Bi- 
ennial Cropping,  and  Green  Manures 
on  the  Yield  of  Wheat. 

273.  Preliminary  Report  on  Kearney  Vine- 
yard Experimental  Drain. 

275.  The  Cultivation  of  Belladonna  in  Cali- 

fornia. 

276.  The    Pomegranate. 

278.  Grain   Sorghums. 

279.  Irrigation  of  Rice  in  California. 

280.  Irrigation  of  Alfalfa  in  the  Sacramento 

Valley. 
283.   The  Olive  Insects  of  California. 

285.  The  Milk  Goat  in  California. 

286.  Commercial    Fertilizers. 

287.  Vinegar  from  Waste  Fruits. 
294.   Bean    Culture   in   California. 

297.  The  Almond  in  California. 

298.  Seedless  Raisin  Grapes. 

299.  The  Use  of  Lumber  on  California  Farms. 
304.   A   study  on   the  Effects  of  Freezes  on 

Citrus    in   California. 

308.  I.  Fumigation  with  Liquid  Hydrocyanic 
Acid.  II.  Physical  and  Chemical  Prop- 
erties of  Liquid  Hydrocyanic  Acid. 

310.    Plum  Pollination. 

312.  Mariout  Barley. 

313.  Pruning  Young   Deciduous  Fruit  Trees. 

316.  The   Kaki   or   Oriental   Persimmon. 

317.  Selections   of   Stocks   in   Citrus   Propa- 

gation. 
319.   Caprifigs  and  Caprification. 
321.   Commercial  Production  of  Grape  Syrup. 
324.   Storage  of  Perishable  Fruit  at  Freezing 

Temperatures. 


No. 

325. 


328. 
331. 
332. 
334. 

335. 

336. 

337. 
339. 

340. 

341. 

342. 
343. 
344. 

345. 

346. 
347. 

348. 
349. 

350. 
351. 
352. 

353. 
354. 
355. 
356. 

357. 


358. 


Rice  Irrigation  Measurements  and  Ex- 
periments in  Sacramento  Valley, 
1914-1919. 

Prune  Growing  in  California. 

Phylloxera-Resistant  Stocks. 

Walnut  Culture  in  California. 

Preliminary  Volume  Tables  for  Second- 
Growth  Redwoods. 

Cocoanut  Meal  as  a  Feed  for  Dairy 
Cows  and   Other  Livestock. 

The  Preparation  of  Nicotine  Dust  as 
an  Insecticide. 

Some  Factors  of  Dehydrater  Efficiency. 

The  Relative  Cost  of  Making  Logs  from 
Small    and    Large    Timber. 

Control  of  the  Pocket  Gopher  in  Cali- 
fornia. 

Studies  on  Irrigation  of  Citrus  Groves. 

Hog  Feeding  Experiments. 

Cheese  Pests  and  Their  Control. 

Cold  Storage  as  an  Aid  to  the  Market- 
ing of  Plums. 

Fertilizer  Experiments  with  Citrus 
Trees. 

Almond    Pollination. 

The  Control  of  Red  Spiders  in  Decidu- 
ous Orchards. 

Pruning  Young  Olive  Trees. 

A  Study  of  Sidedraft  and  Tractor 
Hitches. 

Agriculture  in  Cut-over  Redwood  Lands. 

California  State  Dairy  Cow  Competition. 

Further  Experiments  in  Plum  Pollina- 
tion. 

Bovine  Infectious  Abortion. 

Results  of  Rice  Experiments  in   1922. 

The  Peach  Twig  Borer. 

Observations  on  Some  Rice  Weeds  in 
California. 

A  Self-mixing  Dusting  Machine  for 
Applying  Dry  Insecticides  and 
Fungicides. 

Black  Measles,  Water  Berries,  and 
Related   Vine    Troubles. 


No. 
70.   Observations    on    the    Status    of    Corn 

Growing  in  California. 
82.  The  Common  Ground  Squirrel  of  Cali- 
fornia. 
87.  Alfalfa. 

110.  Green  Manuring  in  California. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali- 

fornia Soils. 
113.   Correspondence  Courses  in  Agriculture. 

126.  Spraying  for  the   Grape  Leaf  Hoppei, 
136.  Melilotus    indica    as    a    Green-Manure 

Crop  for  California. 

127.  House  Fumigation. 

144.   Oidium  or  Powdery  Mildew  of  the  Vine. 
148.   "Lungworms." 

151.  Feeding  and  Management  of  Hogs. 

152.  Some    Observations  on  the  Bulk    Hand- 

ling of  Grain  in   California. 
155.   Bovine  Tuberculosis. 
157.   Control  of  the  Pear  Scab. 

159.  Agriculture  in   the   Imperial   Valley. 

160.  Lettuce  Growing  in  California. 

161.  Potatoes  in   California. 

165.  Fundamentals   of    Sugar   Beet   Culture 

under  California  Conditions. 

166.  The  County  Farm  Bureau. 

167.  Feeding:  Stuffs  of  Minor  Importance. 
169.  The   1918   Grain  Crop. 


CIRCULARS 

No. 
170. 


172. 
173. 

174. 
175. 

178. 
179. 

181. 

182. 

183. 
184. 
188. 
189. 
190. 
193. 
198. 
199. 
201. 
202. 

203. 
205. 


Fertilizing  California  Soils  for  the  1918 

Crop. 
Wheat  Culture. 
The    Construction    of    the    Wood-Hoop 

Silo. 
Farm   Drainage  Methods. 
Progress  Report  on  the  Marketing  and 

Distribution   of  Milk. 
The  Packing  of  Apples  in  California. 
Factors    of    Importance    in    Producing 

Milk  of  Low  Bacterial  Count. 
Control     of     the     California      Ground 

Squirrel. 
Extending  the  Area  of  Irrigated  Wheat 

in   California   for   1918. 
Infectious  Abortion  in  Cows. 
A  Flock  of  Sheep  on  the  Farm. 
Lambing   Sheds. 
Winter  Forage  Crops. 
Agriculture  Clubs   in   California. 
A  Study  of  Farm  Labor  in  California. 
Syrup  from   Sweet   Sorghum. 
Onion  Growing  in  California. 
Helpful   Hints  to   Hog  Raisers. 
County    Organizations   for   Rural    Fire 

Control. 
Peat  as  a  Manure  Substitute. 
Blackleg. 


CIRCULARS — Continued 


No. 

206. 
208. 

209. 
210. 
212. 
214. 

215. 
217. 

218. 

219. 
224. 


225. 
228. 
230. 

232. 

233. 
234. 

235. 

236. 

237. 


No. 

Jack  Cheese.  238. 

Summary  of  the  Annual  Reports  of  the  239. 

Farm  Advisors  of  California. 
The  Function  of  the  Farm  Bureau.  240. 

Suggestions  to  the  Settler  in  California. 
Salvaging  Rain-Damaged  Prunes.  241. 

Seed  Treatment  for  the  Prevention  of 

Cereal   Smuts.  242. 

Feeding  Dairy  Cows  in  California.  244. 

Methods   for  Marketing   Vegetables   in  245. 

California.  246. 

Advanced    Registry    Testing    of    Dairy 

Cows.  247. 

The  Present   Status  of  Alkali.  248. 

Control    of    the    Brown    Apricot    Scale 

and  the  Italian  Pear  Scale  on  Decid-  249. 

uous  Fruit  Trees.  250. 

Propagation  of  Vines. 

Vineyard  Irrigation  in   Arid  Climates.  251. 

Testing  Milk,    Cream,    and    Skim   Milk 

for  Butterfat. 
Harvesting    and    Handling    California  252. 

Cherries  for  Eastern  Shipment.  253. 

Artificial  Incubation.  254. 

Winter  Injury  to  Young  Walnut  Trees 

during  1921-22.  255. 

Soil  Analysis  and  Soil  and  Plant  Inter- 
relations. 256. 
The  Common  Hawks  and  Owls  of  Cali-               257. 

fornia   from    the     Standpoint   of  the  258. 

Rancher. 
Directions  for  the  Tanning  and  Dress- 
ing of  Furs. 


The  Apricot  in  California. 

Harvesting  and  Handling  Apricots  and 
Plums  for  Eastern  Shipment. 

Harvesting  and  Handling  Pears  for 
Eastern   Shipment. 

Harvesting  and  Handling  Peaches  for 
Eastern   Shipment. 

Poultry  Feeding. 

Central  Wire  Bracing  for  Fruit  Trees. 

Vine  Pruning  Systems. 

Desirable  Qualities  of  California  Bar- 
ley for  Export. 

Colonization   and  Rural  Development. 

Some  Common  Errors  in  Vine  Pruning 
and  Their  Remedies. 

Replacing  Missing  Vines. 

Measurement  of  Irrigation  Water  on 
the   Farm. 

Recommendations  Concerning  the  Com- 
mon Diseases  and  Parasites  of 
Poultry    in    California. 

Supports  for  Vines. 

Vineyard   Plans. 

The  Use  of  Artificial  Light  to  Increase 
Winter  Egg  Production. 

Leguminous  Plants  as  Organic  Fertil- 
izer in  California  Agriculture. 

The  Control  of  Wild  Morning  Glory. 

The  Small-Seeded  Horse  Bean. 

Thinning  Deciduous  Fruits. 


